Mix the flour, oatmeal, brown sugar, butter and cinnamon until crumbly. Divide in two.
Press half of the crumb mixture into a 9X13 inch baking pan (greased).
Spread dices apples in pan.
Combine in a small pot, sugar, cornstarch, water and vanilla. Cook on medium heat until the mixture becomes clear and thickened.
Pour over the apples.

Add remaining crumb mixture over top and place baking dish in preheated 350 degree F oven for 30-40 minutes.
You will know when the Apple Crisp is ready by poking the apples which should be soft and the topping should be golden brown.
Serve out onto dishes and top with your favorite ice cream, whip cream, or caramel sauce.